The present invention is generally concerned with postage meters and mailing machines, and more particularly with improvements therein including apparatus for driving a postage meter drum.
In U.S. Pat. No. 2,934,009 issued Apr. 26, 1960 to Bach, et al. and assigned to the assignee of the present invention there is described a postage meter which includes a drive mechanism connected by means of a drive train to a postage meter drum. The drive mechanism includes a single revolution clutch for rotating the drum from a home position and into engagement with a letter fed to the drum. The drum prints a postage value on the letter while feeding the same downstream beneath the drum as the drum returns to the home position. Each revolution of the single revolution clutch and thus the drum, is initiated by the letter engaging a trip lever to release the helical spring of the single revolution clutch. The velocity versus time profile of the peripherary of a drum driven by the clutch approximates a trapezoidal configuration, having acceleration, constant velocity and deceleration portions, fixed by the particular clutch and drive train used in the application. This being the case, the throughput rate of any mailing machine associated with the meter is dictated by the cycling speed of the postage meter rather than by the speed with which the individual mailpieces are fed to the postage meter. Further, although the single revolution clutch structure has served as the workhorse of the industry for many years it has long been recognized that it is a complex mechanism which is relatively expensive to construct and maintain, does not precisely follow the ideal trapezoidal velocity vs. time motion profile which is preferred for drum motion, tends to be unreliable in high volume applications, and is noisy and thus irritating to customers.
Accordingly, an object of the invention is to replace the postage meter drum drive mechanism of the prior art with the combination of a D.C. motor and a computer, and program the computer for causing the D.C. motor to drive the drum in accordance with an ideal trapezoidal-shaped velocity versus time profile which is a function of the input velocity of a mailpiece; and
Another object is to replace the trip lever as the drive initiating device and utilize in its place a pair of spaced apart sensing devices in the path of travel of a mailpiece fed to the postage meter, and program the computer to calculate the input velocity of a mailpiece, based upon the time taken for the mailpiece to traverse the distance between the sensing devices, and adjust the time delay and acceleration of the drum before arrival of the mailpiece at a position at which drum rotation is commenced to cause the drum to timely engage the leading edge of the mailpiece.